As a device to display various images including still images and moving pictures such as PC (personal computer), TV (TV receiver), and others, liquid crystal display devices are popularly used. This kind of liquid crystal display devices are classified into a system to compose a liquid crystal panel of a construction in which a liquid crystal layer is provided between two substrates, basically at least one of which is formed by transparent glass, polymerized film, etc., and carry out switching of the desired pixels (light-on and light-out) by selectively applying voltage to various electrodes for pixel formation formed on the substrate of the liquid crystal panel and a system to form the various electrodes and active elements for pixels selection and switch the desired pixels by selecting this active element. In particular, the liquid crystal display device of the latter system is called an active matrix type and is the mainstream liquid crystal display device because of good contrast performance, high-speed display performance, and others.
For conventional active matrix type display devices, there is a vertical-aligned liquid crystal display in which the electric field is applied across an electrode formed on one substrate and an electrode formed on the other substrate to change the liquid crystal display alignment. In addition, in recent years, a horizontal-aligned liquid crystal display called IPS (In-Plane Switching) has been materialized, in which the direction of electric field applied to the liquid crystal layer is brought nearly parallel to the substrate surface. For an example of this IPS liquid crystal display device, the device designed to obtain a remarkably wide viewing field angle is known by the use of a comb electrode for one of the two substrates (for example, see Japanese Patent Publication No. 63-21907 and U.S. Pat. No. 4,345,249 Specification).
On the other hand, the alignment film that aligns liquid crystal molecules that compose a liquid crystal layer has, in general, microscopic grooves formed in a specific direction by providing treatment called rubbing on the thin film surface such as polyimide-based resin, etc., and has a function to align liquid crystal molecules along these grooves. For the rubbing treatment, a method for forming the alignment film by rubbing the substrate surface with a cloth called rubbing cloth wrapped around a rotating roller has been achieved. In the rubbing process, dust, static electricity, scratches, etc. are generated, which cause a low yield for manufacturing the display and a degradation of display quality.
In particular, in recent years, liquid crystal TV receivers using liquid crystal display devices in place of Braun tube type TV receivers have been popularly utilized and high-quality liquid crystal panels are required. Therefore, in recent years, a technique to get liquid crystal alignment lined up without providing the rubbing treatment to the alignment film has been proposed.
Of the techniques to form the alignment film without providing the rubbing treatment, there is a method to use polarized light. This method is to irradiate a thin film, an alignment film, of polyimide-based resin, etc. with polarized light and to give rise to polarization or structural changes by photochemical reactions. Using optically aligning method, alignment of liquid crystal molecules on the thin film is lined up (this technique is hereinafter called “photo-alignment” technique).
In the photo-alignment method, for the polarized light to be irradiated, ultraviolet rays with high energy are popularly used. FIG. 4 is a drawing that indicates one example of configuration of an apparatus for optically arranging surface of alignment film in order to carry out photo alignment of the alignment film of liquid crystal display device by irradiating the thin film with polarized light, which the present inventors have examined as premises of the present invention. The apparatus for optically arranging surface of alignment film shown in FIG. 4 comprises a lamp (light source) 1, condenser mirror 2, collimator lens 3, polarizer (pile element) 12, integrator lens 6, diffusion lens 7, and others. The light that contains ultraviolet rays and is radiated from lamp 1 is converged at the condenser mirror 2 and is allowed to fall on the collimator lens 3. Parallel beam is formed at the collimator lens 3 and the parallel beam 4 is allowed to fall on the polarizer 12, and polarized light is obtained. And in order to uniformize polarized light distribution, the polarized light is allowed to fall on the integrator lens 6, and the work 100, a component part of liquid crystal display device, etc., is irradiated by the polarized light 9 that passed the diffusion lens 7.
In the above-mentioned photo-induced alignment, for a polarizer 12 to obtain polarized light, resin film with polarization performance, organic film with polarization film affixed to glass, those utilizing a special prism of double reflection, and others are used. In addition, in an apparatus for optically arranging surface of alignment film which comprises the lamp 1, condenser lens 2, and collimator lens 3 and irradiates objects with divergent beam, the polarizer 12 must be disposed in the position with small energy density, that is, the position where light does not condense. This is because the polarizer 12 is exposed to extremely strong light or ultraviolet ray and the polarizer 12 which uses organic film is excessively deteriorated by strong light and ultraviolet ray, and is practically unable to be used at the light converging position.
In addition, even in the event that the polarizer 12 is installed in the region with weak energy density, the organic film is degraded with time against ultraviolet ray, and causes a problem that the polarizer is not applicable for practical use.
On the other hand, the polarizer that uses a prism of double reflection provides resistance to ultraviolet ray but has problems such as inability to be upsized, large incident angle dependence, and others, and is difficult to apply to an exposure apparatus such as an apparatus for optically arranging surface of alignment film.
As described above, there are problems, respectively to apply conventional polarizer to photo-induced alignment of liquid crystal display devices. As against this, polarizer utilizing the Brewster angle (for example, see Japanese Patent Application Laid-Open Publication No. 10-90684) and polarizer using multi-layer films (optical interference films) (for example, see Japanese Patent Application Laid-Open Publication No. 10-332932) are proposed. In the polarizer using the Brewster angle, multiple pieces of glass plates disposed in parallel with spaces are arranged to be inclined to the optical axis by the Brewster angle only. In addition, the polarizer using multi-layer films is a filter with the multilayer film formed on the substrate to polarize the light of a specific wavelength region.